A parked bicycle loaded with explosives blew up as a U.S. army patrol passed by in Afghanistan, slightly injuring two U.S. soldiers, a spokesman said Saturday.

The two soldiers, from the 82nd Airborne Division, suffered minor cuts and bruises, said Col. Roger King at the Bagram Air Base.

The bomb exploded Friday afternoon as the patrol's lead vehicle passed near the U.S. base of Salerno, outside the city of Khost. The base is about 90 miles southeast of the capital, Kabul.

King called the amount of explosive rigged to the bike a "relatively small amount."

"We have had within the past week several improvised explosive devices go off, but they are taking different forms so I don't know if it signifies a trend," King said.

On Wednesday, two Special Forces troops were injured northeast of Jalalabad when anti-tank mines exploded under their vehicle.

On Thursday, a Special Forces soldier was shot in the leg in western Afghanistan when his reconnaissance team came under small arms fire.

Eastern Afghanistan is one of the most active fronts in the U.S.-led campaign against the remnants of Al Qaeda and the Taliban and is regarded as one of the least secure parts of the country.